Add options to customize the cells and the page.

Code example:

    var xlsx = require('node-xlsx');
    var buffer = xlsx.build({ worksheets: [{
      name: 'sheet',
      data: [
        [{
          value: 'example',
          colWidth: 14
        }]
      ]
    }] }, {
      defaultFontName: 'Arial',
      defaultFontSize: 10,
      defaultHAlign: 'center',
      defaultVAlign: 'center',
      defaultCellBorders: { left: '000', right: '000', top: '000', bottom: '000' }, // hex color code
      page: {
        margins: { left: 0.5, right: 0.5, top: 0.5, bottom: 0.5, header: 0.1, footer: 0.1 }, // in inch
        paper_size: 9, // http://msdn.microsoft.com/en-us/library/office/ff839964.aspx
        orientation: 'landscape' // landscape or portrait
      }
    });